1. Field of the Invention
Embodiments of the present invention relates to a display device for reducing a false contour, and a driving method thereof. More particularly, the present invention relates to a display device for reducing a dynamic false contour and improving image quality, and a driving method thereof.
2. Description of the Related Art
Various kinds of flat display devices that are capable of reducing detriments of cathode ray tubes (CRT), such as their heavy weight and large size, have been developed in recent years. Such flat display devices include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and organic light emitting diode (OLED) displays.
Among the above flat panel displays, the organic light emitting diode display using an organic light emitting diode (OLED) generating light by a recombination of electrons and holes for the display of images has a fast response speed, is simultaneously driven with low power consumption, and had excellent luminous efficiency, luminance, and viewing angle such that it has been spotlighted.
In general, a plurality of pixels emitting light in the organic light emitting diode display include an organic light emitting diode, and the organic light emitting diode generates light of a predetermined luminance corresponding to a data current supplied from a pixel circuit.
Digital driving which is one of gray expression methods of the organic light emitting diode display controls an on time of a pixel. In the case of the organic light emitting diode display that follows the digital driving method, one frame is divided into a plurality of sub-frames, and a light emitting period of each sub-frame is appropriately set in order to display a gray. The pixel emits light during a sub-frame selected depending on an image signal for gray expression among the plurality of sub-frames constituting one frame. That is, the sub-frame selected according to the image signal is turned on to express the grayscale.
However, according to the digital driving (sub-frame mode), in a case where a motion picture is played, or the observer's eye to observe still images is moved, light of the previous frame and the current frame between the adjacent pixels is overlapped and observed by the observer's eye. Then, bright or dark grayscales, which are not desired grayscales for representation, are displayed. This is called a dynamic false contour phenomenon.
Recently, a method for weakening intensity of the dynamic false contour phenomenon by increasing a number of sub-frames has been adapted for the purpose of improving the dynamic false contour phenomenon, but the method requires a higher driving frequency so it has a restriction in application. Further, additional image processing such as dithering or error diffusion has been used to improve the dynamic false contour phenomenon, which is, however, difficult to integrate into a drive IC of medium to small displays. Therefore, studies for improving the problem of failing to express desired grayscales because of the dynamic false contour phenomenon are needed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.